Milk: the new sports drink?
Brian D Roy
Centre for Muscle Metabolism and
Faculty of Applied Health Sciences, Brock University,
St. Catharine's, Ontario, Canada
article and references are here..
Being a Scientific Paper, (and not written by simple old
me) this is a little heavier than our normal factsheets, as it uses a
lot of big words and contains some very long sentences. I've
re-formatted it but changed none of the content. Stick with it, it
contains some good info that may help you in your quest to be a better
The photo above will bring
a tear to the eye of those of us of a certain age. For the young 'uns
it'll mean little; you don't know what you missed ~ woollen jerseys, toe
clips, hairnet helmets and not a black sock to be seen; sniff....
People still laugh (disbelievingly) when I tell them it was in the rule
book that shorts had to be black and socks had to be white, it's true!
Ten points if you can name
the rider, another ten for the year and one point if you can name the
race! Click the photo for the answer.
Nutritional intake is important for optimizing sport and
exercise performance. Furthermore good nutrition is important in
optimizing adaptations to training. For example, the ancient
Greeks believed that high protein intakes were important for athletes,
and these athletes would consume diets that contained excessive amounts
Such ideas are still
pervasive today, especially with resistance based sports such as body
building. It is common for resistance athletes to consume diets
that are more than double the recommended levels of dietary protein.
In addition, athletes who participate in body building and similar
sports are bombarded with marketing for various supplements, many of
which are very high in protein.
Research has clearly
demonstrated that such excessively high protein intakes aren't necessary
to facilitate the adaptations that occur with resistance training.
Research has also established that the timing of nutritional intake is
also very important in optimizing the adaptations to this form of
exercise, as well as recovery from both resistance and endurance
the nutrient composition of post-exercise nutritional intake has also
been shown to be important in the recovery from endurance exercise and
adaptations/recovery from resistance exercise.
Bovine based milk and milk
products represent a very good source of proteins, lipids, amino acids,
vitamins and minerals. The health benefits of milk have been well
established and have been extensively reviewed elsewhere.
Low-fat milk has a number of
characteristics that theoretically make it a potentially good recovery
(Table 1). Firstly, it contains carbohydrates (lactose) in
amounts similar to many commercially available sports drinks (glucose,
Milk contains casein and whey
proteins in a ratio of 3:1 which provides for slower digestion and
absorption of these proteins resulting in sustained elevations of blood
amino acid concentrations. Another advantage is that whey protein also
contains a large proportion of branched chain amino acids which have an
integral role in muscle metabolism and protein synthesis.
Finally, milk also has
naturally high concentrations of electrolytes, which are naturally lost
through sweating during exercise. The high concentrations of these
electrolytes should aid in fluid recovery following exercise. Based on
these characteristics of milk, there has been growing sport nutrition
research interest in milk and its possible roles as an exercise beverage
for both resistance and endurance sports and training.
Resistance Exercise & Training
Resistance exercise and resistance sports are characterized by repeated
high intensity contractions of varying muscle groups that leads to well
characterized adaptations in muscles.
The most obvious adaptation
is skeletal muscle hypertrophy. For muscle hypertrophy to occur
there must be a chronic increase in muscle protein net balance.
Muscle protein balance is a function of muscle protein synthesis and
muscle protein breakdown. Thus, for an increase in net balance to
occur, there must be an increase in protein synthesis, a decrease in
muscle protein breakdown or simultaneous increase in synthesis and
decrease in breakdown. (Obviously!!!??? ~ TW)
Over the last decade there
has been considerable investigation into the influence of various
factors that influence the protein metabolism response to resistance
Resistance exercise alone
results in both an increase in protein synthesis and protein breakdown,
but the increase in synthesis is greater than the increase in breakdown,
resulting in a less negative net balance.
Interestingly, the results
from Phillips et al. did show a less negative protein balance, but the
net balance was still negative since participants were in a fasted
state. These observations emphasised the importance of supplying
macronutrients for influencing protein metabolism following exercise.
Several studies have
documented the provision of macronutrients soon after resistance
exercise in an attempt to optimize the protein metabolic response.
Intake of amino acids, protein, carbohydrates, or mixed macronutrient
compounds contribute to enhanced protein metabolism following resistance
This work has documented that
the protein-related metabolic response following resistance exercise can
be influenced through the nutritional intake of the main macronutrient
constituents of low-fat milk; protein and carbohydrates. Follow-up
studies have directly investigated the impact of milk consumption on the
acute protein metabolic response following resistance exercise.
Elliot et al. investigated
the influence of consuming differing milk beverages on the protein
metabolic response following an acute bout of resistance exercise.
They compared the influence of non-fat milk (237 g), whole milk (237 g)
and an amount of non-fat milk with the same amount of energy (kJ) as the
whole milk condition (393 g) following a bout of leg resistance
They assessed amino acid net
balance across the exercise leg for 5 hours following the leg resistance
exercise. All of the different milk beverages resulted in a significant
increase in net balance of the measured amino acids. This study
did not determine what contributed to the change in net balance (change
in synthesis, change in breakdown, or both), however, the evidence did
show that protein metabolism was enhanced with a single bolus intake of
milk after the resistance exercise.
Recent work has shown that
one way by which consumption of fat-free milk increase protein net
balance is through an increased rate of muscle protein synthesis
following resistance exercise. The increase in protein net balance
and muscle protein synthesis was most pronounced with the consumption of
500 mL of fat-free milk as compared to an isoenergetic, isonitrogenous,
and macronutrient matched soy-protein beverage (745 Kj, 18.2 g protein,
1.5 g fat, and 23 g carbohydrate).
The authors speculated that
their observations were attributable to the differences in soy protein
digestion as compared to milk protein digestion. The soy based
beverage was digested and absorbed much more rapidly leading to a large
rapid rise in blood concentrations of amino acids shuttling them to
plasma protein and urea synthesis.
with the fat-free milk the elevation in blood amino acids was slower and
remained elevated for a more prolonged period, providing a more
sustained delivery of amino acids for skeletal muscle protein synthesis.
Therefore, it is reasonable
to hypothesize that milk beverages, when consumed soon after resistance
exercise, can lead to enhanced improvements in protein metabolism
following resistance exercise.
Such acute increases in
protein net balance and synthesis could possibly enhance the more
chronic adaptations that occur with resistance training. Based on
the acute changes in protein metabolism with milk consumption following
resistance exercise, a number of questions arise.
Firstly, what would be the
application of this information over the long term and secondly, how can
this be applied to athletes who are training on a regular basis.
Recent research has addressed the long term influence of milk
consumption after resistance training.
Studies ~ #1
The first study to investigate the interaction of resistance
training and milk consumption over a more prolonged period compared the
effects of 3 days per week (for 10 weeks) of progressive resistance
training with consumption of either low-fat chocolate milk (5 kcal/kg
body weight) (composition described in table
1) or a commercially available carbohydrate and electrolyte beverage
(5 kcal/kg body weight) within 5 min of completing each workout.
The post-exercise beverages
contained the same amount of energy, but varied in macronutrient
(Table 2). The training resulted in improvements in strength and
body composition, however all of these changes where similar between the
no differences were observed for any of the measured variables when the
group that consumed milk post exercise was compared to the group that
consumed the commercial sports drink.
However, there was an
interesting trend for the milk group to have a greater increase in
fat-free soft tissue mass. The milk group gained 1.6 ± 0.4 kg of
fat-free soft tissue mass, while the carbohydrate electrolyte beverage
group only gained 0.8 ± 0.5 kg of fat-free soft tissue mass.
These observations were not
significantly different, but it would have been interesting to observe
what would have occurred if the protocol had have been extend to see if
these differences would have been more pronounced. Nonetheless,
this was the first study to look at the long term interaction of milk
consumption and resistance training.
Studies ~ #2
More recently, Hartman et al. compared the
consumption of three different post resistance exercise beverages during
an extended period of intense resistance training in novice
The three different beverage
conditions were; 1) fat-free milk (500 mL), 2) a soy beverage (500 mL)
that was isoenergetic, isonitrogenous and macronutrient ratio matched to
the fat-free milk, and 3) a control beverage (500 mL) that consisted of
a flavoured carbohydrate beverage that contained maltodextrin.
The participants were
randomized into the three different groups and trained 5 days per week
for 12 weeks and consumed the appropriate beverage immediately and one
hour following completion of each training session.
Interestingly, consumption of
the fat-free milk resulted in greatest increases in muscle hypertrophy,
as observed through greater increases in both type I and II muscle fibre
areas. They also observed that the group that consumed the milk
also gained the most lean body mass over the duration of the study.
Fat mass also declined to the
greatest extent in the milk group. The authors attributed the
greater increase in muscle fibre hypertrophy and lean mass to the
previously observed acute influences of milk consumption on protein
The greater decline in fat
mass observed with the milk group was suggested to be related to the
greater calcium intake associated with the milk consumption, as there is
growing evidence to suggest a pivotal role for dairy products in
influencing adipocyte metabolism in a manner that attenuates lipid
This very well controlled
study clearly showed multiple benefits to using fat-free milk as a
post-resistance exercise beverage.
There is growing amounts of
evidence, both acute and long-term, to support the use of low-fat milk
as a post-resistance exercise beverage. Consumption of low-fat
milk appears to create an anabolic environment following resistance
exercise and over the long term with training, it appears that greater
gains in lean mass and muscle hypertrophy can be obtained.
Furthermore, milk may also
lead to greater losses of body fat when it is consumed following
Endurance Exercise & Training
Endurance sports and activities are generally considered to be
sub-maximal activities that can be performed for more prolonged periods
These activities are also
characterized by continuous exercise and activity that is highly
dependent on oxidative metabolism as a source of energy and usually
involve large muscle groups.
This dependence on oxidative
metabolism and involvement of a large muscle mass leads to higher rates
of total substrate turnover and under certain conditions, depletion of
muscle glycogen in the active muscles. However, there can be
considerable differences in the responses observed depending on the
intensity of the exercise performed.
From a nutritional
standpoint, there are three primary times when nutrition is considered
for endurance based activities;
during exercise, and
Each time period of
nutritional concern has varying objectives. Prior to exercise,
nutritional goals are to ensure that the athlete is well fuelled and
that any nutritional intake will not interfere with the normal
physiological responses to the activity.
The goal of nutritional
intake during exercise is to provide exogenous substrates in an attempt
to delay the depletion of endogenous substrates, and to provide fluids
to offset fluid losses due to sweating.
Finally, the nutritional
objectives of post-exercise nutrition are to promote muscle recovery and
adaptations, fuel resynthesis in muscle, and fluid replenishment.
With specific regard for the
role of milk as a nutritional option for endurance activities, there is
limited research into the possible benefits of milk and it is also
difficult to extend findings into any consistent recommendations because
of differences in design and methodology.
However, a number of recent
studies suggest that there is significant potential for expanded
research in this area, especially in the area of recovery from endurance
v Sports Drinks
What is evident is that when milk is compared to carbohydrate
based sports drinks, similar responses in many physiological variables
are observed during the exercise.
have been some minor differences reported such as increased
concentrations of essential amino acids, based on the protein content of
milk. Interestingly, when milk is consumed during prolonged
exercise, following completion of the exercise a reduction in whole body
protein breakdown and protein synthesis was observed with a simultaneous
increase in protein oxidation.
Even, Hero's drink milk.
The authors speculated that
the decrease in whole body protein synthesis might have been due to
preferential oxidation of the ingested protein during the exercise,
leaving less amino acids available for synthesis after the exercise.
Another difference that has
been reported is that participants reported greater feelings of stomach
fullness with milk as compared to water or carbohydrate based beverages.
The increase in stomach fullness possibly suggests that the rate of
fluid intake may have been greater than gastric emptying, which would
not have been unexpected as the rate of gastric emptying declines with
increasing energy density of the fluid consumed.
Despite these reported
variations in physiological responses and stomach fullness, there were
no reported differences in actual performance measures. For
example, when participants rode at a set intensity until exhaustion,
milk and carbohydrate based sports drinks resulted in similar times to
exhaustion, suggesting that milk is just as beneficial as commercially
available sports drinks at delaying the onset of fatigue under these
Clearly, additional research
is required to further establish the efficacy of milk as an endurance
exercise supplement beverage.
Future research should
include time trial based performance measures, as they are more
realistic to endurance sport performance. Furthermore, future
research should also strive to develop a greater understanding of the
metabolic influence of milk consumption during prolonged exercise, as
there is very limited research in this area.
v Recovery Drinks
The use of milk as a recovery beverage after endurance
exercise has also been investigated to a limited extent.
The main goal of any post
exercise nutritional intervention is usually to promote muscle glycogen
resynthesis, and fluid recovery. In regards to glycogen
resynthesis, there is very limited direct research into the efficacy of
milk consumption to replenish muscle glycogen levels.
However, there is some
performance based data that suggests that chocolate milk is as effective
as a commercially available sports drink in facilitating recovery (See
Table 3 for drink composition).
group of trained endurance athletes were used to compare the
effectiveness of varying endurance recovery beverages, one being
chocolate milk, following a series of glycogen depleting intervals. The
chocolate milk drink and the carbohydrate recovery drink were controlled
based on carbohydrate and energy content.
After four hours of recovery
and consumption of the different beverages, the participants performed a
ride to exhaustion. The time to exhaustion and total work
performed during the performance trial was the same when the
participants consumed chocolate milk or a common commercially available
Based on these findings one
could speculate that chocolate milk may be as effective as more commonly
used sports drinks at promoting glycogen resynthesis. However, to
date there have been no well controlled studies that have directly
measured the efficacy of milk to promote muscle glycogen recovery
following prolonged endurance exercise.
Therefore, future research
should directly quantify rates of muscle glycogen resynthesis following
prolonged endurance exercise and compare the efficacy of milk to other
commonly used recovery beverages.
There is growing scientific evidence to
support the use of low-fat milk following exercise by both individuals
and athletes who habitually undertake strength or endurance training.
There is data which suggests
that fat free milk is as effective as, and possibly even more effective
than, commercially available sports drinks at promoting recovery from
strength and endurance exercise.
Further work is required to
better understand the physiological mechanisms by which milk exerts its
actions following exercise and training.
Milk also has the added
benefit of providing additional nutrients and vitamins that are not
present in commercial sports drinks.
In conclusion, fat free
milk is a safe and effective post-exercise beverage that has been shown
to promote recovery from exercise and should be considered as a viable
alternative to commercial sports drinks by lactose tolerant individuals.
There has been growing interest in the potential use of bovine milk as
an exercise beverage, especially during recovery from resistance
training and endurance sports.
Based on the limited
research, milk appears to be an effective post-resistance exercise
beverage that results in favourable acute alterations in protein
metabolism. Milk consumption acutely increases muscle protein
synthesis, leading to an improved net muscle protein balance.
Furthermore, when post-exercise milk consumption is combined with
resistance training (12 weeks minimum), greater increases in muscle
hypertrophy and lean mass have been observed.
Although research with milk
is limited, there is some evidence to suggest that milk may be an
effective post-exercise beverage for endurance activities. Low-fat
milk has been shown to be as effective, if not more effective, than
commercially available sports drinks as a rehydration beverage.
Milk represents a more
nutrient dense beverage choice for individuals who partake in strength
and endurance activities, compared to traditional sports drinks.
Bovine low-fat fluid milk is a safe and effective post exercise beverage
for most individuals, except for those who are lactose intolerant.
Further research is warranted
to better delineate the possible applications and efficacy of bovine
milk in the field of sports nutrition.
© 2008 Roy; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.